This invention relates generally to a radio receiver, and in particular, it relates to a novel combination of a traffic radar receiver, a scanning receiver for the public service radio bands, and a receiver for the citizen band.
The convenience and safety of highway travel is enhanced by the use of a number of items of electronic equipment that are now available. One of these is the traffic radar receiver, which provides an indication of the presence of traffic radar that is in use of the vicinity of the traveler. A second is a scanning receiver for the public service radio bands, which alerts the listener to broadcasts affecting highway conditions and the availability of police, fire, and ambulance units. A third is a receiver for broadcasts on the citizen band (CB). Separate units are available commercially to handle each of these functions. Thus, it is possible to obtain a separate traffic radar receiver for use in a vehicle. It is also possible to obtain a scanning receiver that covers the public service bands and that is adaptable for use in a vehicle. Moreover, it is possible to obtain a receiver for the citizen band that can be used in vehicles. However, the cost of three such individual units becomes considerable, and the amount of space required in a vehicle for all three such units can present storage and handling problems.
In addition, most scanning receivers for public-service bands have a limited number of frequencies that are set to match those in use in a particular area. Frequencies for public-service bands are typically assigned by the Federal Communications Commission for individual states. The traveler who crosses from one state into another thus finds a need to change the frequencies that are scanned. This typically requires maintaining a table of the frequency assignments and manually changing scanned channels for the new state.
An additional problem common to radar receivers, portable scanning receivers for public-sevice bands, and receivers for the citizen band is that such items attract thieves if left in the passenger compartment of a vehicle. One solution to this problem has been to make the items of equipment portable so that they can be removed from the passenger compartment. One such unit is easy to handle, but two or three present complications. Another particular problem is presented if the items of equipment are to be powered from the power supply of the vehicle, as through a cigarette lighter socket. As a result, it is common to use battery-powered radar receivers and to make permanent installations of CB units that combine transmitters and receivers. However, the battery-powered units present the possibility of battery failure at an inopportune time, and the use of separate units for scanning traffic radar, receiving public service bands, and monitoring the citizen band leads to the duplication of components and functions that increase the total cost of such equipment.